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Show ~46 IMBEDDING OF REMAIN· s OF REPTILES AND BIJ;tDS, [Ch. XV. ] t · peat 0 f tl1 e sa me locality ' the elytra of beetles In the acus rme . but in the deposits of drained lakes gene-are not uncommon ' f t aries the relics of this class of rally' and in ~he silt o our ~ts umely 'rare. In the blue. clay of h · 1 km o·dom are ex re tv eer ammomdae rn oroi gin of Lewes L eve 1s , Mr. Mant.e ll has found h YI d · r cases of t h e 1a rv re of Phryganea, m abundance, tw iet h nm iunsuiat,e os hells b e1 o ng.m g to the genera Planorbis, Lim-nea &c., adhering to them*. . . W' hen speak 'm g of the migrations of msects, wed pomtbed out that an I. mmen~,e numh er are floated into lakes an seas y . bl by· winds far from the land; but they are so rl vers or own r buoya' nt t 11 at we can o nly suppose them, under very pecu. h1 ar circumstances, to sm. k t 0 the bottom before they are eit er devoured by insectivorous animals or are decomposed. Remains of Reptiles. As the bodies of several crocodiles were found in. the m.ud brought down to t h e sea by the river inund6a tiOn which attended an earthquake in Java in the year 1 99:flwe ~ay ima ine that extraord m. ary . fl oo ds, of mud may st1. e ma.n y . d'g. duals of the shoals of alligators and other reptiles whiCh m 1 Vl · • • t · al climates f . t lakes and the deltas of rivers m ropiC . requen 1 . b t amonO' the Thousands of frogs were found eapipg a o.u . o wrec k carn.e d m. t o the "~' ea by the late ·i nundatiOn.s m· Morday ~ h. t . and it is evident that whenever a sea-cliff .IS un ers 1re , 1 · to the sea mined, or land is swept by other vio ent causes m ' land reptiles may be carried in. Remains of Birds. ~W E might have anticipated that t 11 e I·m b ed dm' g of the remai£n s of birds in new strata woul d b e of very 1· are o. ccu. rrence, 1or their powers of flight insure them against penshm~ lr~:merous casualties to which quadrupeds are expose g * Trans. Geol. Soc·. vol. m... . part 1· · P· 201 ' Second Series. t Sir T. D. Lauder's 'Account, Second Ed.,y. 312. Ch.XV.] IMBEDDING OF TERRESTRIAL QUADRUPEDS. ~47 floods; and if they chance to be drowned, or to die when swimming on the water, it will scarcely ever happen that they will be submerged so as to become preserved in sedimentary deposits. For in consequence of the hollow tubular structure of their bones and the quantity of their feathers, they are extremely light in proportion to their volume, so that when :first killed they do not sink to the bottom like quadrupeds, but float on the surface until the carcass either rots away or is devoured by predaceous animals. To these causes we may ascribe the absence of any vestige of the bones of birds in the recent marl formations of Scotland; although these lakes, until the moment when they were artificially drained, were frequented by a great abundance of water-fowl. Imbedding of Terrestrial Quadrupeds. RivEu. inundations recur in most climates at very irregular intervals, and expend their fury on those rich alluvial plains where herds of herbivorous quadrupeds congregate together. 'rhese animals are often surprised, and being unable to stem the current, are hurried along until they are drowned, when they sink immediately to the bottom. Here their bodies are drifted along, together with sediment, into lakes or seas, and may then be covered by a mass of m~d, sand, and pebbles, thrown down upon them. If there be no sediment superimposed, the gases generated by putrefaction usually cause the bodies to rise again to the surface about the ninth, or at most the fourteenth day. The pressure of a thin covering would not be sufficient to retain them at the bottom, for we see the putrid carcasses of dogs and cats, even in rivers, floating with considerable weights attached to them, and they would be still more buoyant in sea-water. In cases where the body is so buried in drift-sand, or mud accumulated upon it, as never to rise again, the skeleton may be preserved entire; but if it comes again to the surface while in the process of putrefaction, the bones commonly fall |